F150 fuel pressure issue

I have a 2005 f150 that seems to be having some fuel pressure issues. The boat will start fine, and run fine at higher rpms. The problem I am having is when at idle to barely moving, I seem to be losing some fuel pressure. For example, I launched yesterday and the engine started immediately. I left it running while I parked the truck and got set-up. When i went to put it into gear to pull away from the dock, it shut off. I went and pumped the bulb, which was soft, a few times and it started right up and ran fine. When i am slowly moving the engine often loses some pressure and i must periodically pump the bulb a little to keep it running. It sounds like a clogged filter somewhere. I am about to change the fuel/water separator, but I am not sure what other filters I should check. Is it more than a filter issue? i know the only way to really know is to change the filters and see if that fixes the problem. The engine runs great, but this is a little annoying. Thanks for the help!

Plugged Filter

Had exact same symptoms on my 250 a few weels ago. The fuel/water seperator filter was clogged. Changed the filter and engine runs perfectly. First time I have ever had one of those filters plug. Had about 70 hours of operation on it. I think the E-10 gas caused it. Going back to real gas.

Thanks you! went to the local boat dealer, Merritt Marine in Hillsborough, this afternoon looking for advice. I would just like to say that I don't not know these people, but they are always more than willing to help me whenever I stop by. Please, if you need some work done and you live in the Chapel Hill area, look them up, they are excellent at customer service. Anyway, I talked with the owner about my problem. He gave me a clear piece of tubing with a nipple and told me to splice it into the fuel line near the engine. If there are bubbles in this line, there is an air leak in the fuel system somewhere. If not, then it may be a filter/hose problem. I'm hoping to try it out this weekend once I get home from school. I'll let you guys know what happens. I am also going to replace my fuel/water filter with a new 10 micron system (mine still has the 30 micron filter). Though this is a little nerve racking, I am somewhat enjoying learning more about my engine and how to diagnose/handle problems. What they told me today probably saved me $100 bucks from having it serviced. Hopefully the problem will be an easy fix and not a fuel pump issue...we shall soon see

I likewise suspected the fuel/water filter and it will soon be replaced as well, thanks again for your help!